Method of fabricating liquid crystal display device

ABSTRACT

A method for forming a display device, includes forming a thin film transistor (TFT), a gate pad and a data pad on a substrate; depositing sequentially an inorganic insulating material and an organic insulating material on the substrate having the TFT, the gate pad and the data pad; selectively removing the organic insulating material using a diffracting mask to form a patterned organic insulating layer; selectively removing the inorganic insulating material, using at least a portion of the patterned organic insulating layer as a mask to define contact holes for the TFT, the gate pad and the data pad; and forming electrodes in the contact holes.

This application is a Divisional of application Ser. No. 10/278,931,filed Oct. 24, 2002 now U.S. Pat. No. 6,650,380.

The present application claims, under 35 U.S.C § 119, the benefit ofKorean Patent Application No. P2001-081774 filed Dec. 20, 2001, which isherein fully incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to a liquid crystal display, and moreparticularly to a method of fabricating a liquid crystal display devicethat has improved yield.

2. Description of the Related Art

Generally, a liquid crystal display (LCD) controls the lighttransmissivity of liquid crystal cells arranged in a matrix pattern inresponse to a video signal to thereby display a picture corresponding tothe video signals on a liquid crystal display panel. To this end, theLCD includes a liquid crystal display panel having liquid crystal cellsarranged in an active matrix, and driving integrated circuits (IC's)drive the liquid crystal cells.

The driving IC's are usually manufactured in chip form. The driving IC'sare mounted on a tape carrier package (TCP) film attached to the outerperiphery of the liquid crystal panel. The driving IC's are connected bya tape automated bonding (TAB) system while being mounted along the edgeof the liquid crystal panel, when they are connected by a chips on glass(COG) system. In the TAB system, the driving IC's are electricallyconnected to a pad portion provided at the liquid crystal panel by meansof the TCP.

FIG. 1 is a plan view showing a structure of a conventional LCD device.

In FIG. 1, the LCD device has a lower plate 4 and an upper plate 6 thatoppositely adhere to each other. The LCD device includes a picturedisplay part 2 having liquid crystal cells arranged in a matrix pattern,and gate pad portions GP and data pad portions DP connected between thedriving IC's and the picture display part 2.

In the picture display part 2, data lines supplied with data signals andgate lines supplied with gate signals are arranged at the lower plate 4so as to cross each other. Each of the crossing parts is provided with athin film transistor for switching the liquid crystal cell, and a pixelelectrode connected to the thin film transistor drives the liquidcrystal cell. The upper plate 6 includes coated color filters, and thecolor filters are separated for each cell area by black matrices. Acommon transparent electrode is coated on the surfaces of the colorfilters. Upper and lower plates 6 and 4 are spaced from each other by aspacer to provide a cell gap, which is filled with a liquid crystalmaterial. The upper and lower plates 6 and 4 adhere to each other bymeans of a sealant coated on a seal 10 at the outside of the picturedisplay part 2.

The edge area of the lower plate 4 that does not overlap with the upperplate 6 is provided with gate pad portions GP and data pad portions DP.The gate pad portion GP applies a gate signal from the gate driving ICto the gate line of the picture display part 2. The data pad portion DPapplies a video signal from the data driving IC to the data line of thepicture display part 2.

In the LCD device having the structure described above, a protectivefilm for protecting the metal electrode and the thin film transistorsentirely coats the lower plate 4. The pixel electrode is formed on theprotective film for each cell area. The protective film is an organicprotective film that enhances the aperture ratio of the pixel.

As shown in FIG. 2, a gate pad 14 of the gate pad portion GP along witha gate line of the picture display part 2 is provided on a lowersubstrate 1. A gate insulating film 22 and an organic protective film 24are sequentially entirely coated on the lower substrate 1 to cover thegate pad 14. A gate contact hole 16 a is formed by patterning the gateinsulating film 22 and the organic protective film 24 to expose aportion of the gate pad 14. A gate protective electrode 20 is formed onthe organic protective film 24 to electrically connect the gate pad 14to the gate protective electrode 20 via the gate contact hole 16 a.

As shown in FIG. 3, a data pad 18 of the data pad part DP along with adata line of the picture display part 2 are provided on the gateinsulating film 22. The organic protective film 24 entirely coats thegate insulating film 22 to cover the data pad 18. A data contact hole 16b forms by patterning the organic protective film 24 to expose a portionof the data pad 18. A data protective electrode 26 formed on the organicprotective film 24 is electrically connected, via the data contact hole16 b, to the data pad 18.

The gate pad portion GP and the data pad portion DP are in contact withthe TCP mounted with the driving IC by the TAB system. The gate pad 14and the data pad 18 are electrically connected to the TCP via the gateprotective electrode 20 and the data protective electrode 26 provided onthe organic protective film 24. This has the goal of preventing damageto the gate pad 14 and the data pad 18 upon repetition of the TCPadhering process required for the TAB system. Also, the gate pad 14 andthe data pad 18 are not exposed and hence do not react with peripheralmoisture to cause their oxidative corrosion.

In order to electrically connect the TCP to the gate protectiveelectrode 20 and the data protective electrode 26, an anisotropicconductive film 12 as shown in FIG. 4A and FIG. 4B is provided. Theanisotropic conductive film 12 is coated with conductive particles 28,which form a current path between the TCP, the gate protective electrode20 and the data protective electrode 26.

If the data pad portion DP and the gate pad portion GP adhere to the TCPmounted with the driving IC by the TAB system, then it is necessary torepeat the process of adhesive bonding and separating the TCP many timeswhen defects caused by a misalignment occur. Accordingly, as the organicprotective film 24 has a weak adhesion characteristic with respect tothe gate insulating film 22, it is removed along with the TCP in theprocess of separating the TCP. In this case, there is a problem in thatunevenness of the surface removed with the organic protective film 24causes a weak adhesion characteristic upon re-adhering the TCP.

Furthermore, if the organic protective film 24 on the gate pad 14 andthe data pad 18 is removed, then the gate protective electrode 20 andthe data protective electrode 26 thereon also are removed. Accordingly,there is a problem in that the gate pad 14 and the data pad 18 areexposed to be damaged or oxidized, thereby deteriorating thecharacteristics of the gate pad 14 and the data pad 18.

Moreover, if a mask for eliminating the residual organic protective film24 is used for a smooth repair process, then the productivity is reducedand hence a production time is prolonged.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a method offabricating a liquid crystal display device that is adapted to improvethe yield and overcome problems and disadvantages of the related art.

A method of fabricating a liquid crystal display device according to anembodiment of the present invention, includes forming a gate electrodeand a gate pad over a substrate, forming a gate insulating film over thesubstrate, forming a semiconductor layer over the gate insulating film,forming a source electrode, a drain electrode and a data pad over thegate insulating film, depositing an inorganic insulating material overthe gate insulating film, depositing an organic insulating material overthe inorganic insulating material, removing selectively the organicinsulating material at a partial area over the drain electrode, the gatepad and the data pad to leave a portion of the organic insulatingmaterial over the gate pad and the data pad, patterning the inorganicinsulating material using at least a portion of the remaining organicinsulating material as a mask, thereby providing an organic protectivefilm and a part of an inorganic protective film over the source anddrain electrodes and a part of the inorganic protective film over thegate and data pads, and forming a transparent electrode pattern over theinorganic protective film and the organic protective film.

A method of fabricating a liquid crystal display device according to anembodiment of the present invention, includes forming a gate electrodeand a gate pad over a substrate, forming a gate insulating film over thesubstrate, forming a semiconductor layer over the gate insulating film,forming a source electrode, a drain electrode and a data pad over thegate insulating film, depositing an inorganic insulating material on thegate insulating film, depositing an organic insulating material over theinorganic insulating material, removing selectively the organicinsulating material at a partial area over the drain electrode, the gatepad and the data pad, to leave a portion of the organic insulatingmaterial over the gate pad and the data pad, patterning the gateinsulating film and the inorganic insulating material using at least aportion of the remaining organic insulating material as a mask, therebyproviding an inorganic protective film, an organic protective film, adrain contact hole, a gate contact hole and a data contact hole, andforming a pixel electrode on the inorganic protective film by depositinga transparent conductive film onto the inorganic protective film and theorganic protective film and patterning the transparent conductive film,and forming a gate protective electrode and a data protective electrodeon the inorganic protective film.

A method for forming a display device according to an embodiment of thepresent invention, includes forming a thin film transistor (TFT), a gatepad and a data pad on a substrate, depositing sequentially an inorganicinsulating material and an organic insulating material on the substratehaving the TFT, the gate pad and the data pad, selectively removing theorganic insulating material using a diffracting mask to form a patternedorganic insulating layer, selectively removing the inorganic insulatingmaterial, using at least a portion of the patterned organic insulatinglayer as a mask to define contact holes for the TFT, the gate pad andthe data pad, and forming electrodes in the contact holes.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects of the invention will be apparent from thefollowing detailed description of the embodiments of the presentinvention with reference to the accompanying drawings, in which:

FIG. 1 is a schematic plan view showing a structure of a conventionalliquid crystal display device;

FIG. 2 is a section view of the gate pad portion shown in FIG. 1;

FIG. 3 is a section view of the data pad portion shown in FIG. 1;

FIG. 4A and FIG. 4B illustrate anisotropic conductive films provided onthe gate pad portion and the data pad portion shown in FIG. 2 and FIG.3, respectively;

FIG. 5 is a plan view showing a structure of a liquid crystal displaydevice according to an embodiment of the present invention;

FIG. 6 is a section view of the liquid crystal display device takenalong the A-A′, B-B′ and C-C′ lines in FIG. 5;

FIG. 7 illustrates examples of masks positioned at the upper portions ofthe gate pad portion and the data pad portion shown in FIG. 6; and

FIG. 8A to FIG. 8G are section views showing a method of fabricating theliquid crystal display device shown in FIG. 6 according to an embodimentof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Advantages of the present invention will become more apparent from thedetailed description given herein after. However, it should beunderstood that the detailed description and specific examples, whileindicating preferred embodiments of the invention, are given by way ofillustration only, since various changes and modifications within thespirit and scope of the invention will become apparent to those skilledin the art from this detailed description.

FIG. 5 and FIG. 6 show a liquid crystal display (LCD) device accordingto an embodiment of the present invention.

As shown, the LCD device includes a picture display part TP havingliquid crystal cells arranged in a matrix pattern. Gate pad portions GPand data pad portions DP are connected between driving IC's (not shown)and the picture display part TP.

The picture display part TP has data lines 34 supplied with datasignals, and gate lines 32 supplied with gate signals are arranged at alower plate (not shown) to cross each other. Each of the crossing partsis provided with a thin film transistor (TFT) for switching the liquidcrystal cell and having a gate electrode 36, a source electrode 38 and adrain electrode 40. An inorganic protective film 48 protects the TFT,and an organic protective film 62 enhances the aperture ratio. A pixelelectrode 52 in electrical contact with the drain electrode through adrain contact hole 50 b is provided on the organic protective film 62for each cell area.

The gate pad portion GP is connected to a gate driving IC (not shown)positioned at one end of the gate line 32. The gate pad portion GPapplies a gate signal for controlling the TFT from the gate driving ICto the gate line 32 of the picture display part TP. The gate pad portionGP includes a gate pad 54 connected to the gate line 32, and a gateprotective electrode 58 connected to the gate driving IC. The gateinsulating film 42 and the inorganic protective film 48 are providedbetween the gate pad 54 and the gate protective electrode 58.

The data pad portion DP is connected to a data driving IC (not shown)positioned at one end of the data line 34. The data pad portion DPapplies a data signal for controlling the TFT from the data driving ICto the data line 34 of the picture display part TP. The data pad portionDP includes a data pad 56 connected to the data line 34, a dataprotective electrode 60 connected to the data driving IC, and theinorganic protective film 48 provided between the data pad 56 and thedata protective electrode 60.

FIG. 7 shows a grating 64 having one or more diffraction parts and atransmission part that are positioned at the gate pad portion GP and thedata pad portion DP of the LCD device. This grating 64 is used in a maskwhich is used to pattern the layers of the LCD device. To accomplishthis, the transmission part of the grating 64 is positioned tocorrespond with an area provided with a gate contact hole 50 a over thegate pad 54 and a data contact hole 50 c over the data pad 56. Thediffraction part of the grating 64 has a relatively small width and ispositioned to correspond with an area other than the gate contact hole50 a and the data contact hole 50 c. Thus, since the gate pad portion GPand the data pad portion are not provided with the organic protectivefilm 62, the inorganic protective film 48 protects the gate pad portionGP and the data pad portion DP. The TFT of the picture display part TPis protected by the inorganic protective film 48 and the organicprotective film 62 for enhancing an aperture ratio.

The organic protective film 62 corresponding to the data pad portion DPand the gate pad portion GP of the LCD device is entirely removed toprevent removal of the gate protective electrode 58 and the dataprotective electrode 60 caused by a weak adhesion characteristic of theorganic protective film 62 upon repetition of the TAB process. Further,an anisotropic conductive film for adhering the gate pad portion GP andthe data pad portion DP to the TCP is in direct contact with theinorganic protective film 48 to enhance an adhesive force of the TAB.

FIG. 8A to FIG. 8G show a method of fabricating the LCD device shown inFIG. 6 using a diffraction mask having a grating according to anembodiment of the present invention.

In FIG. 8A, a gate metal layer is deposited on the substrate 31 by adeposition technique such as sputtering. In one embodiment, the gatemetal layer is made from at least one of aluminum(Al), copper(Cu), etc.Then, the gate metal layer is patterned by the photolithographyincluding an etching process to provide the gate pad 54 and the gateelectrode 36 on the substrate 31.

In FIG. 8B, the gate insulating film 42 is formed on the substrate 31provided with the gate pad 54 and the gate electrode 36. The gateinsulating film 42 is made from an inorganic insulating material such assilicon oxide (SiO_(x)), silicon nitride (SiN_(x)), or siliconoxynitride (SiOxNy). First and second semiconductor layers arecontinuously deposited on the gate insulating film 42 by a chemicalvapor deposition (CVD) technique or other suitable technique. The firstsemiconductor layer is formed from undoped amorphous silicon. The secondsemiconductor layer is formed from amorphous silicon doped with ann-type or p-type impurity such as boron, phosphorous, arsenic, etc.Then, the first and second semiconductor layers are patterned by thephotolithography including a dry etching process, e.g., plasma etch, toprovide an active layer 44 and an ohmic contact layer 46.

In FIG. 8C, a data metal layer is deposited on the gate insulating film42 provided with the active layer 44 and the ohmic contact layer 46 by aCVD technique, sputtering or any other suitable technique.

The data metal layer is made from, e.g., chromium (Cr), molybdenum (Mo),etc. Then, the data metal layer is patterned by photolithographyincluding a wet etching process to provide the data pad 56, the sourceelectrode 38 and the drain electrode 40. Subsequently, the ohmic contactlayer 46 exposed between the source electrode 38 and the drain electrode40 is removed by a dry etching process or any other suitable process toseparate the source electrode 38 and the drain electrode 40. A portionof the ohmic contact layer 40 is removed, and hence a portioncorresponding to the gate electrode 36 between the source and drainelectrodes 38 and 40 at the active layer 44 makes a channel.

In FIG. 8D, an inorganic insulating layer 48 a is formed on the gateinsulating film 42 of the substrate 31 provided with the data pad 56,the source electrode 38 and the drain electrode 40. The inorganicinsulating layer 48 a is made from an inorganic material, preferablyfrom silicon nitride (SiN_(x)).

An organic insulating layer 62 a is formed on the substrate 31 providedwith the inorganic insulating layer 48 a.

The organic insulating layer 62 a is made from an organic insulatingmaterial such as an acrylic or methacrylic organic compound, isoprenecompound, phenol-formaldehyde resin, benzocyclobutene (BCB) or PFCB(perfluorocyclobutane). In one embodiment, the organic insulating layer62 a is made preferably from acrylic photoresist. The acrylicphotoresist can be a negative resist material and can be chemicallyenhanced.

An example in which acrylic photoresist is used as the organicinsulating layer 62 a will be described below.

A diffracting mask 66 is positioned at the upper portion of thesubstrate 31 provided with the acrylic photoresist 62 a. The diffractingmask 66 has a grating 64 forming a diffraction part 66 a and atransmission part 66 b, and a shielding part 66 c. The transmission part66 b of the diffraction mask 66 is positioned at an area where a gatecontact hole, a data contact hole and a drain contact hole is to be madelater. The diffraction part 66 a is positioned at an area of the gatepad portion GP and the data pad portion DP excluding the gate contacthole and the data contact hole. The shielding part 66 c is positioned atthe other area.

In FIG. 8E, the diffracting mask 66 positioned at the upper portion ofthe substrate 31 is used to expose and develop the acrylic photoresist62 a. The acrylic photoresist 62 a is removed from an area correspondingto the transmission part 66 b of the diffracting mask 66 by an exposureand development process, thereby exposing portions of the inorganicinsulating layer 48 a. The acrylic photoresist 62 a equal to about 10%to 50% of its initial thickness is left at an area corresponding to thediffraction part 66 a while the acrylic photoresist 62 a equal to itsinitial thickness is left at an area corresponding to the shielding part66 c.

In FIG. 8F, according to an embodiment of the present invention, theremaining acrylic photoresist 62 a is used as a mask to remove portionsof the inorganic insulating layer 48 a so as to form contact holes 50 band 50 c, and to remove portions of the inorganic insulating layer 48 aand the gate insulating film 42 so as to form a contact hole 50 a.Thereafter, a certain thickness of the acrylic photoresist 62 a isremoved, which results in the organic protective film 62 over the TFTregion, but not over the gate and data pads 54 and 56. This processproduces the inorganic protective film 48, the organic protective film62, the gate contact hole 50 a, the drain contact hole 50 b and the datacontact hole 50 c formed on the substrate 31. Thus, the inorganicprotective film 48 is provided at an area other than the gate contacthole 50 a, the drain contact hole 50 b and the data contact hole 50 c,and this area excludes the transmission part 66 b of the diffractingmask 66. The organic protective film 62 is formed on the TFT of thepicture display part TP, which is an area corresponding to the shieldingpart 66 c of the diffracting mask 66. The gate contact hole 50 a, thedrain contact hole 50 b and the data contact hole 50 c are formed at anarea corresponding to the transmission part 66 b of the diffracting mask66.

In accordance with another embodiment, instead of completely removingthe organic protective film 62 over the gate and data pads 54 and 56after the contact holes 50 a, 50 b and 50 c are defined, the presentinvention performs these two steps simultaneously. That is, while theportions of the patterned organic protective film 62 over the gate anddata pads 54 and 56 and TFT are being removed (or etched away from thetop to bottom), the remaining portions of the patterned organicprotective film 62 over the gate and data pads 54 and 56 and TFT areused as a mask to form the contact holes 50 a, 50 b and 50 c. An ashingtechnique, a dry etching, and/or other known suitable technique may beused in these processes.

In FIG. 8G, a transparent electrode layer is formed on the organicprotective film 62 and the inorganic protective film 48 by a depositiontechnique such as sputtering. The transparent electrode layer is madefrom indium-tin-oxide (ITO), indium-zinc-oxide (IZO) orindium-tin-zinc-oxide (ITZO), etc. Then, The transparent electrode layeris patterned by photolithography, including an etching process toprovide the pixel electrode 52, the gate protective electrode 58 and thedata protective electrode 60. The pixel electrode 52 is electricallyconnected to the drain electrode 40 via the drain contact hole 50 b,which passes through the organic protective film 62 and the inorganicprotective film 48. The gate protective electrode 58 electricallyconnects to the gate pad 54 via the gate contact hole 50 a, which passesthrough the gate insulating film 42 and the inorganic protective film48. The data protective electrode 60 electrically connects to the datapad 56 via the data contact hole 50 c, which passes through theinorganic protective film 48.

As described above, according to an embodiment of the invention, theorganic protective film of the pad portion is removed by the diffractionand exposure. Accordingly, a removal of the transparent electrode layercaused by a weak adhesion characteristic of the organic protective filmupon repetition of the TAB process can be prevented. Hence a damage andan oxidization of the pad portion caused by the removal of thetransparent electrode layer can be prevented.

Also, the anisotropic conductive film is in direct contact with theinorganic insulating layer by the entire removal of the organicprotective film of the pad portion, so that the adhesive force of theTAB can be enhanced. Furthermore, a repair-effectiveness of the tapecarrier package is improved to enhance the yield and productivity.

It is to be understood that the foregoing descriptions and specificembodiments shown herein are merely illustrative of the best mode of theinvention and the principles thereof, and that modifications andadditions may be easily made by those skilled in the art withoutdeparting for the spirit and scope of the invention, which is thereforeunderstood to be limited only by the scope of the appended claims.

1. A method for forming a display device, comprising: forming a thinfilm transistor (TFT), a gate pad and a data pad on a substrate;depositing sequentially an inorganic insulating material and an organicinsulating material on the substrate having the TFT, the gate pad andthe data pad; selectively removing the organic insulating material usinga diffracting mask to form a patterned organic insulating layer;selectively removing the inorganic insulating material, using at least aportion of the patterned organic insulating layer as a mask to definecontact holes for the TFT, the gate pad and the data pad; selectivelyremoving the patterned organic insulating layer as the organicinsulating material is removed in the step of selectively removing theinorganic insulating material; and forming electrodes in the contactholes.
 2. The method of claim 1, further comprising: removing thepatterned organic insulating layer corresponding to the gate and datapads after the step of selectively removing the inorganic insulatingmaterial is performed.
 3. The method of claim 1, further comprising:providing a gate insulating layer under the inorganic insulatingmaterial; and selectively removing portions of the gate insulating layercorresponding to the gate and data pads, using said at least a portionof the patterned organic insulating layer as a mask.
 4. The method ofclaim 1, wherein, in the step of forming the electrodes, the electrodesinclude an electrode in contact with the gate pad and the remaininginorganic insulating material, and an electrode in contact with the datapad and the remaining inorganic insulating material.
 5. The method ofclaim 1, wherein an ashing technique is employed in removing the organicinsulating material.
 6. The method of claim 1, wherein a dry etchingtechnique is employed in removing the organic insulating material.